Side wing blade assemblies are extensively used on snow plow vehicles. A typical side wing blade arrangement includes an elongated curved blade and an articulated attachment system for mounting the blade to the vehicle. Typically, a mounting system comprises a coupling for connecting the front end of the blade to a vehicle, and an articulated hanger unit for connecting the rear end of the blade to the vehicle chassis and also for tilting the wing between a plowing position and a retracted position. In the plowing position, the blade extends at an angle to the longitudinal axis of the vehicle engaging the road surface, while in the retracted position it is lifted up and extends generally parallel and close to the vehicle cabin.
Many different mounting systems have been tried over the years with changes from steel cables running over sheaves or pulleys to a variety of hydraulic cylinder systems. One such hydraulic cylinder actuated system is shown in Farrell U.S. Pat. No. 4,045,892. This includes a pair of generally vertical posts mounted on the side of the vehicle on which the front and rear of the side wing blade are attached. Not only are the posts intrusive, but with this design, when the blade is in the retracted position, it seriously interferes with the visibility of the vehicle driver.
The assembly shown in Canadian Patent 1,212,540 represents one attempt at solving the problem of obstructed vision. This still utilizes vertical post arrangements for connecting the front end and rear end of the blade to the vehicle. However, the mounting arranging on the vertical posts has been changed such that the blade in retracted position sits at a lower angle to avoid obstructing view of the vehicle driver.
In Thorneloe, U.S. Pat. No. 4,969,280 there is described a side wing assembly having a rear mounting arrangement which permits a controlled blade deflection to reduce the risk of damage to the snow plow or to the side wing assembly itself, when the blade hits an obstacle. This is accomplished by a fluid ram with stops limiting the amount of movement.
Raines et al. Canadian Patent 1,082,545 describes a retractable snow plow wing which does not use a vertical post for the rear attachment assembly. Instead, a telescopic arm is used which can be fixed at different lengths. The raising and lowering of the arm and rear end of the blade is accomplished by way of a hydraulic cylinder. A coil compression spring is utilized in association with the telescopic arm to absorb shock. The design of this patent is another one which seriously obstructs the view of the vehicle driver when the blade is in the retracted position.
It is an object of the present invention to provide an improved form of side wing plow assembly having a novel form of front mounting for the blade.
It is a further object of the present invention to provide an improved form of rear mounting for the blade which includes a novel shock absorbing linkage.